Role of glycosylation in the lipid-binding activity of the exchangeable apolipoprotein, apolipophorin-III.
Non-glycosylated recombinant Locusta migratoria apolipophorin-III, apoLp-III, was expressed in E. coli and its physical-chemical properties were compared to those of the glycosylated native apoLp-III. Fluorescence quantum yield and acrylamide quenching studies indicated a slightly higher accessibility of the Trp residues in the recombinant apoLp-III. Far-UV CD spectroscopy indicated that the recombinant apoLp-III has a lower alpha-helical content than the glycosylated apoLp-III. Both proteins spontaneously formed discoidal recombinant lipoprotein particles when incubated with dimyristoylphosphatidylcholine (DMPC). Interaction with lipid promotes an increase in alpha-helical content. CD and fluorescence studies indicate that both proteins adopt the same conformation in the lipid-bound state. However, the kinetics of association of the recombinant protein with DMPC is 5-fold faster than that of the native protein. The results suggest that glycosylation inhibits the lipid binding activity by preventing the exposure of hydrophobic domains and/or decreasing the conformational flexibility of the protein.
Soulages
J L
JL
Department of Biochemistry, University of Arizona, Tucson 85721, USA.
Pennington
J
J
Bendavid
O
O
Wells
M A
MA
D000818:Animals; D001053:Apolipoproteins / Q000737:chemistry*; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D006031:Glycosylation; D006110:Grasshoppers; D007700:Kinetics; D050356:Lipid Metabolism; D008055:Lipids / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000235:genetics
D001053:Apolipoproteins; D008055:Lipids; D011994:Recombinant Proteins; C042470:apolipophorin III; D004134:Dimyristoylphosphatidylcholine